FIG. 1 is a cross-sectional view showing the structure of a conventional flooring for an under-floor heating system in which a natural veneer is laminated on a waterproof plywood. As shown in FIG. 1, the conventional flooring has a structure wherein a natural veneer layer 22 is surface-coated with a UV coating paint to form a general UV coating layer 21′, or is resin-impregnated and then laminated over a waterproof plywood layer 10′ through an adhesive layer 40.
However, disadvantages of the conventional flooring for an under-floor heating system include poor scratch resistance and impact resistance under a certain load. Specifically, the conventional flooring has a surface scratch resistance as low as 0.5˜1N, which is measured by scratching the flooring using a diamond needle, and an impact resistance as low as 5 cm, which is measured by dropping a metal ball weighing 228 g onto the flooring. These low values indicate that the conventional flooring is easily impaired when household appliances are laid thereon and used. Accordingly, there is a large possibility that the conventional flooring causes consumer complaints and cannot satisfy diverse needs of consumers. There is, thus, a need for a flooring having improved scratch resistance and impact resistance.
As other conventional floorings, there have been widely known floorings which are manufactured by attaching a decorative veneer (printed paper) to plywood and coating the laminate, or laminating plywood and a medium-density fiberboard (MDF) to each other, joining a decorative veneer to the MDF and coating the laminate. Representative examples of these floorings are manufactured by attaching a decorative sheet (printed paper) to plywood, or laminating plywood and MDF to each other and attaching a decorative sheet (printed paper) to the medium-density fiberboard of the laminate.
The former floorings, however, have the problem of poor caster resistance. In addition, in the case where tongues and grooves are formed on the floorings, naps and edge splits may occur on which yams of socks and stockings are often snagged and raveled out. On the other hand, since the latter floorings have the problem that MDF is swollen by permeation of water because the MDF has poor water resistance, sometimes impairing the design of the floorings, as in the use of wood-made decorative veneer (printed paper).
Further, the use of a medium-density fiberboard having superior physical properties to plywood is advantageous in terms of caster resistance but causes problems of poor water resistance and occurrence of peeling when immersed in water.
Thus, there exists a need for the development of a wood flooring as a low-price construction material having a stabilized dimensional variation against temperature changes while satisfying required physical properties, e.g., caster resistance and water resistance.